Passenger car seat back adjusters having toothed ratchet and pawl positioning in 3.degree. increments are known in the art; for example, as disclosed in U.S. Pat. No. 3,999,247 and copending application Ser. No. 945,303. It is also known to achieve finer steps of adjustment through the provision of a translation overdrive linkage between the seat back and the toothed ratchet so that the arcuate movement of the ratchet segment may be substantially double the angular movement of the seat back thereby achieving for example 11/2.degree. increments of seat back adjustment with 3.degree. ratchet teeth.
The provision of still finer increments of adjustments through the use of finer pitch teeth has been limited by the tolerances involved in the extremity stop positions combined with the possibility of pawl and ratchet teeth being blocked from full engagement at the extremity positions thereby causing malfunction and possible damage to the respective teeth upon application of loads to the seat back.